This invention relates to liners or inflations for teat cup assemblies for vacuum-operated automatic milking machines for milk producing animals.
Automatic milking machines employ teat cup assemblies having a hollow, rigid outer shell and a resilient, tubular liner or inflation installed in the shell in a manner to form a seal at both ends of the shell and define a chamber between the shell and the inflation.
Inflations include an upper portion or suction sleeve which fits inside the teat cup shell and a lower portion or milking tube section. In one-piece inflations, the milking tube section is formed integrally with the suction sleeve and extends from an opening in the lower end of the teat cup shell and is adapted to be connected to the nipple of a so-called claw of the milking machine. In multi-piece inflations, the suction sleeve and the milking tube section are separate parts and are connected in fluid communication with each other by a sleeve connector or the like or the milking tube section includes a cup-shaped upper end which fits over the lower end of the teat cup shell with the upper end in fluid communication with the interior of the suction sleeve.
An animal's teat is inserted into the upper end of the inflation. During the milking operation, the teat cup assembly is suspended from a teat by engagement between an opening or mouth in the upper or head end of the inflation and also with the inside surface of the suction sleeve. A vacuum maintained in the milking machine claw causes the teat orifice to dilate, allowing milk to flow from the teat, through the suction sleeve and through the milking tube section into the milker claw. The chamber between the shell and the suction sleeve is connected to a pulsator on the milking machine. The pulsator periodically opens the shell chamber to atmospheric pressure, causing the suction sleeve to collapse to a closed position. When in this closed position, the suction sleeve compresses the teat tissue and causes the teat orifice to close, interrupting flow of milk from the teat. Flow of milk from the teat resumes when the suction sleeve returns to a normally open position in response to the pulsator subsequently connecting the shell chamber to vacuum.
Desirable features for a suction sleeve include (1) an internal configuration which permits a teat cup to be slipped onto a teat far enough to minimize slippage during milking and maintain the teat cup on the teat until milking has been completed, (2) capability of providing a substantially balanced closing action on a teat while collapsing in response to the pulsator opening the shell chamber to atmospheric pressure, (3) capability of rapidly returning from a collapsed or closed position to a normally opened position in response to the pulsator connecting the shell chamber to the vacuum, thereby maximizing the milk flowing period and minimizing the total milking time, and (4) capability of withstanding extended close/open cycles without structural failures.
Suction sleeves typically have a circular inside configuration. As a teat shrinks in diameter during milking, the area of surface contact between the teat and the inside surface of suction sleeves having such a configuration can result in a decrease of frictional forces to a point where the teat cup drops downwardly on a teat from the original milking position, and even drops off a teat in some cases, before milking is completed.
Animals teats tend to assume the shape of the interior of the suction sleeve during milking. A suction sleeve having a triangular cross section provides more surface area contact with a teat than a circular one and thereby reduces slippage. However, the flat walls of triangular suction sleeves tend to collapse faster to a closed position in response to the pulsator opening the shell chamber to atmospheric pressure and return more slowly to a normally open position in response to the pulsator connecting the shell chamber to a vacuum, resulting in less of the total time interval of a pulsation cycle being available for milking.
French Patent No. 499,796 discloses configuring the interior of the shell so that, during the milking cycle, portions of the suction sleeve are in close contact with the shell interior and can not expand or bulge while other portions are spaced inwardly from the shell interior and can expand or bulge to a limited degree. FIG. 3 of the patent discloses a generally triangular shell having undulating sides and arranged to prevent expansion or bulging of portions of the suction sleeve adjacent the side walls. Only portions of the suction sleeve in the vicinity of the three corners of the triangle can expand or bulge.